1. Technical Field
The present disclosure relates to a concentrated photovoltaic device that is capable of generating thermal and electrical energy from solar radiation using a three-dimensional (3-D) solar cell design structure with no need for a sun-tracking system.
2. Description of the Related Art
The concentrated photovoltaic (CPV) solar cell design's use of silicon material brings about the advantages of overall cost reduction and power conversion efficiency. Many CPV solar cell systems use highly efficient monocrystalline or polycrystalline silicon solar cells with a light collecting lens such as Fresnel lens, a plastic convex lens, or a lens duct. These lenses focus solar radiation into the solar cell to generate electricity. The current problem with CPV solar designs, however, is that the solar cell has to face the solar rays directly to generate adequate amounts of electricity. As a result, many current designs have incorporated a tracking system which follows the Sun to maximize the conversion efficiency. Typically, the tracking system is a relatively expensive component. Furthermore, its mechanical nature makes it an implicitly unreliable component over many years of continuous operation. A novel three-dimensional solar cell structure removes the need for a tracking system and allows for the collection of all solar rays without the need to track the movement of the Sun. This design will improve long term reliability and reduce the total system cost.
In the case of CPV design, the solar cell has to maintain a certain temperature range to maintain the optimum electrical conversion efficiency. The cooling of the CPV design is another important factor in achieving long term reliability of the solar cell and maximum energy efficiency. Currently, many designs have been developed with a heat-fin or other structure mounted to the solar cell frame to cool the solar cell to a certain temperature; without such structures, the solar cell performance would be degraded when the solar cell exceeds a certain temperature threshold. In this invention, we have designed a liquid cooling scheme for the 3-D solar cell to maintain an optimal operating temperature for the CPV solar cell. In addition, the thermal solar energy coming from the liquid cooling is recycled to heat a hot-water tank.
The captured solar energy can be converted into both electricity and thermal energy. The shorter wavelengths of the solar spectrum (e.g. ultra-violet) can be converted into electricity while the longer wavelengths (e.g., infrared) can be converted into thermal energy. Because the thermal energy is also absorbed into the solar cell, a large heat sink is often used to cool off the solar cell in CPV designs and the solar cell loses its efficiency as the temperature rises beyond a certain threshold. This invention will utilize not only the shorter wavelength to generate electricity but also extract and store the thermal energy generated by the longer wavelengths into a hot-water reservoir. This scheme will improve the solar energy conversion efficiency of the CPV solar cell design to the highest conversion efficiency by utilizing both electrical and thermal energy derived from the incident solar energy.